In middle of redacting a VIEW that deals with groups, members, and precedence, i fixed a bug, and explained a line in greater detail with (what i think is) the correct logic. (The actual COLUMN name has been shortened):

-- Match this record:
-- To match INDIVUDAL, check P_ as C_ will be NULL (INDIVUDALs have no children).
-- To match GROUP, check C_ for the children; parents can be ignored.
-- (Note: Checking the NULL child or irrelevant parent should not be a problem.)
AND PHC_1.C_ IN (PHC_2.P_, PHC_2.C_)